Heating, ventilating, air conditioning, and refrigeration noise reduction system

ABSTRACT

Embodiments of a noise reduction system for use in heating, ventilating, air conditioning, and refrigeration (HVACR) systems are provided. The noise reduction system may include a barrier to be placed over an air inlet of an HVACR base unit. The barrier, consisting of two rows of equally spaced structures, may permit the passage of air therethrough while preventing the escape of noise from the base unit. The noise reduction system may also include one or more resonance chambers placed atop the base unit and a structure placed adjacent the base unit. Noise coming from the base unit may be redirected by the structure toward the resonance chambers, which are configured to attenuate the noise.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Non-Provisional Patent Application of U.S. Provisional Patent Application No. 61/409,816, entitled “Noise Reduction Methods for Modular Heating, Ventilating, Air Conditioning, and Refrigeration Systems”, filed Nov. 3, 2010, which is herein incorporated by reference.

BACKGROUND

The invention relates generally to heating, ventilation, air conditioning, and refrigeration (HVACR) systems, and, more particularly, to noise reduction methods for modular HVACR systems.

HVACR systems are utilized for a variety of applications that require the temperature and quality of surrounding air to be regulated. For example, HVACR systems are utilized to provide ventilation, to filter air, and to maintain desirable pressure relationships for buildings, aircraft, and so forth. For further example, HVACR systems may be provided on a ground support equipment cart to serve aircraft parked at gates. As such, HVACR systems typically include a main system blower and various heat exchangers that cooperatively function to output a desired air stream.

HVACR systems may generate large amounts of noise, especially when driven at high airflow volume. Such noise is generated primarily from refrigeration compressors, condenser fans, and the main system blower. Sound waves propagate from these components and enter the surroundings, escaping the HVACR system through the main system blower air inlets and condenser fan inlets. Such noise output to the surroundings may lead to an undesirable increase in noise pollution, and, therefore, it may be beneficial to apply appropriate noise reduction techniques to these systems.

Certain noise reduction techniques, however, may not be appropriate for use with HVACR systems. For example, typical sound proofing walls, if positioned directly over the air inlets, could block air from being drawn in through the inlets. This could create a pressure drop that negatively affects the performance of the main blower or the condenser fans. In addition, portable HVACR systems (e.g., modular AC units used on a ground support equipment cart) would likely benefit from noise reduction techniques that could be incorporated into the system unit, in order to maintain portability of the overall system. Accordingly, there exists a need for an HVACR noise reduction system that may be incorporated into the HVACR system while also allowing appropriate airflow.

BRIEF DESCRIPTION

In an exemplary embodiment, an air conditioning noise reduction system includes a base unit with an air inlet on one surface and at least one fan in the unit. The at least one fan is used to draw air into the unit through the inlet and to output the air toward a downstream process. A barrier including two rows of spaced structures is placed over the inlet to allow passage of air through the barrier into the unit but to prevent noise caused by the fan from escaping the unit.

In another embodiment, an air conditioning noise reduction system includes a first row of spaced structures, a second row of spaced structures, and one or more edges coupled to the structures of both rows. The structures of both rows redirect noise caused by a blower in an air conditioning unit, and the structures of one row overlap the spaces between structures of the other row. The edges may be coupled to the air conditioning unit, allowing air to be drawn in through the spaces between the rows by the blower.

In a further embodiment, an air conditioning noise reduction system includes a base unit with at least one fan in the base unit and one or more resonance chambers placed adjacent to an air inlet of the base unit. A structure positioned outside the base unit redirects noise caused by the fan toward the resonance chambers, which are designed to attenuate the noise.

DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view of an exemplary modular air conditioning (AC) unit in accordance with aspects of the present invention;

FIG. 2 is a top view schematic of the AC unit of FIG. 1 with a noise reduction system preventing noise from escaping the unit;

FIG. 3 is a side cross sectional view of an exemplary barrier of the noise reduction system of FIG. 2 allowing air to pass through the barrier but preventing noise from passing through the barrier;

FIG. 4 is a perspective view of the barrier of FIG. 3 with reticulated foam arranged on the barrier to absorb noise;

FIG. 5 is a side cross sectional view of a barrier including two rows of parallel plates with reticulated foam;

FIG. 6 is a side view of the AC unit of FIG. 1 with a noise reduction system for attenuating noise from a condenser fan;

FIG. 7 is a side view of the condenser unit and certain components of the noise reduction system of FIG. 6 with a scoop-shaped structure to redirect sound waves from the condenser fans; and

FIG. 8 is a front view of a punched hole plate for use in the noise reduction system of FIG. 6.

DETAILED DESCRIPTION

Turning now to the drawings, FIG. 1 is a perspective view of a modular air conditioning (AC) unit 10, which includes a blower module 12 including louvers (air inlet) 14 and an internal controller 15, a condenser module 16, and an evaporator module 18 including louvers 20. The condenser module 16 includes a first fan 22, a second fan 24, and louvers 26, although additional fans may also be provided, for example, a third fan and a fourth fan located on a back side of the condenser module 16. A hose connection 28, which may couple the modular AC unit 10 to a downstream device (e.g., an aircraft), is coupled to the evaporator module 18 in the illustrated embodiment, but may be located in any suitable location on the modular AC unit 10 in other embodiments.

During operation, the modular AC unit 10 is adapted to receive incoming air, condition such air, and output the conditioned air for use in a desired downstream application. For example, in one embodiment, the modular AC unit 10 may be located on a ground support equipment cart for an aircraft and, accordingly, may output the conditioned air to an associated aircraft via connection 28. As such, the modular AC unit 10 may be adapted to function as a refrigeration circuit, thus receiving ambient air and outputting cooled air. To that end, during use, the blower unit 12 receives and circulates incoming air. The condenser module 16 and the evaporator module 18 cooperate to function as a heat exchanger module. For example, the blower module 12, the condenser module 16, and the evaporator module 18 function in a refrigeration cycle, which utilizes a vapor-compression cycle to generate conditioned air. In such embodiments, the condenser module 16 receives a refrigerant and subsequently removes heat from the refrigerant by condensing the vaporized refrigerant into a liquid. Additionally, the evaporator module 18 vaporizes a received refrigerant, absorbing heat due to the latent heat of vaporization and cooling the ambient air moved over the evaporator coils by the blower.

It should be noted that different arrangements of the AC unit 10 may be possible, as will be appreciated by those skilled in the art. For example, multiple condenser modules 16 and evaporator modules 18 may be combined in series adjacent a single blower unit 12 in order to achieve a desired air output capacity. For further example, the AC unit 10 may be a split level unit, featuring a condenser module 16 that is positioned a distance away from the evaporator module 18 and the blower unit 12. Additionally, the blower unit 12 may feature an air inlet 14 on a surface of the blower unit 12 opposite the downstream process to which the air is being moved, streamlining the directional flow of air through the AC unit 10.

Certain components of the AC unit 10 may produce relatively large amounts of noise. Such noise may be caused by the operation of a blower in the blower unit 12 or by the blower interacting with air moving through the blower unit 12. Without a noise barrier, this noise may exit the AC unit 10 through the inlet 14 and enter the surroundings. The condenser module 16 may also be a source of noise escaping into the surrounding environment, as operation of the first fan 22 and the second fan 24 may generate additional noise.

FIG. 2 illustrates the movement of air and noise through certain portions of the AC unit 10. The movement of air is indicated by arrows 30, 32, 34, 36, 38, 40, and 42. Arrows 30 and 32 indicate air being drawn through the inlet 14 by a blower 44 in the blower unit 12. In the illustrated embodiment, the blower 44 includes a first fan 46 and a second fan 48, which propel the air from the blower unit 12 toward the evaporator module 18, as indicated by arrows 34 and 36. As will be appreciated by those skilled in the art, the blower 44 may feature a different number of fans, depending on the size and application of the blower unit 12. Alternatively, the blower 44 may be a radial tip pressure blower capable of outputting air at higher airflow volumes and pressures. Once propelled by the blower 44 into the evaporator unit 18, as indicated by arrows 38 and 40, the air passes over evaporator coils (not shown) before exiting the AC unit 10 via the hose connection 28. Conditioned to a desired temperature and air speed, the air then moves toward a downstream process, as indicated by arrow 42. The downstream process may include any heating, ventilating, air conditioning, or refrigeration application for which the conditioned air is desired.

In addition to passing through the inlet 14, air passes through a noise reduction barrier 50 placed over the inlet 14 in FIG. 2. The barrier 50 may include a first row of spaced structures 52 and a second row of spaced structures 54, both rows attached to each other and to the blower unit 12 with two edges 56 and 58. The rows of structures 52 and 54, which may be constructed from sheet metal, are designed to redirect noise 60 while allowing air to pass through. Such noise 60 may propagate from the blower 44, caused by the mechanical operation of the fans 46 and 48 or the interaction of the fans with air traveling through the blower unit 12. As shown in FIG. 2, air continues to pass through the barrier 50 and enter the blower unit 12 through the inlet 14, while noise 60 generated by the fans 46 and 48 is redirected by the barrier 50. This may allow dissipation of the noise 60 to occur inside the blower unit 12, instead of outside the AC unit 10 where the noise 60 could disturb the surroundings.

It should be noted that the barrier 50 may be placed over the inlet 14 to the blower unit 12 in addition to, or in lieu of, louvers, which are shown on the AC unit 10 in FIG. 1. Louvers are generally used to allow air to pass into the unit while preventing some particles from being introduced into the unit and some level of noise from escaping. The barrier 50, which includes rows of overlapping structures 52 and 54, may be as effective as louvers at preventing particles from entering the blower unit 12 and more effective at preventing noise 60 from escaping the blower unit 12. Therefore, the barrier 50 may be placed over already existing louvers of an AC unit 10 or built into an AC unit 10 as a cover over the inlet 14.

A detailed cross sectional side view of one noise barrier 50 arrangement is provided in FIG. 3. Air moves from the right side to the left side of barrier 50, as indicated by arrows 30, 32, and 34, the left side representing the inside of the blower unit 12 and the right side representing an area outside the AC unit 10. The rows of structures 52 and 54 are arranged vertically, the structures of the first row 52 aligning with spaces between the structures of the second row 54. The structures in the illustrated embodiment are equally spaced and feature equivalent cross sections, but other arrangements are possible as well. Each structure in the two rows 52 and 54 includes two side surfaces 62 to further prevent noise 60 from escaping through the barrier 50. The rows 52 and 54 may be arranged such that their respective side surfaces 62 interleave to form a channel 64 between the rows 52 and 54. Air may pass freely through the barrier 50, entering through spaces between structures in the first row 52, moving through the channel 64 formed by the side surfaces 62, and entering the blower unit 12 through spaces between structures in the second row 54. The size of the spaces between the structures and the channel 64 may be optimized to mitigate an airside pressure drop according to the maximum airflow volume of the blower unit 12.

Noise 60 produced by the blower 44 approaches from the blower unit 12 side of the barrier 50 in FIG. 3. Upon reaching the barrier, the waveforms of the noise 60 may be reflected off the structures of the second row 54. When a waveform of noise 60 approaches a space between the structures of the second row 54, the waveform may enter the channel 64, reflecting off the side surfaces 62 or the first row structures 52. Repeated reflection may cause the noise 60 to dissipate, thereby significantly reducing any noise 60 that eventually exits through the spaces between the first row structures 52. Therefore, the barrier 50 prevents the large amount of noise 60 caused by the blower 44 from escaping the blower unit 12 and disrupting the environment.

FIG. 4 illustrates the same arrangement of rows of structures 52 and 54 described in FIG. 3, but with layers of reticulated foam 66 added to certain surfaces of the structures. This figure also shows the horizontal extension of the two rows of structures 52 and 54, connected by the edge 58 at one end. Edges may connect the two rows 52 and 54 at one or more ends, or even at one or more intervals between the ends of the structures, to provide structural support and to secure the barrier 50 to the blower unit 12. Reticulated foam 66 may be added to one or more surfaces of the structures in order to absorb the noise 60 coming from the blower 44. When the noise 60 contacts the reticulated foam 66, which features an open cell structure, noise energy may be at least partially converted into heat and vibration within the foam 66, thereby lessening the noise 60. The foam 66 may offer additional noise reduction to the barrier 50, further reducing the noise output to the surrounding environment.

It should be noted that not all surfaces of the rows of structures 52 and 54 illustrated in FIG. 4 include reticulated foam 66. The foam 66 is shown placed on larger surfaces of the rows 52 and 54 facing the left as well as the surfaces of the second row 54 facing the right side. This placement of foam 66 may be particularly effective since the noise 60 would likely bounce off at least one of these surfaces in order to escape the blower unit 12. Other combinations of surfaces for applying reticulated foam 66 are possible as well. In addition, the thickness of the foam 66 placed on these surfaces may vary depending on the amount of noise absorption desired, the dimensions of the rows of structures 52 and 54, and space needed for moving air through the barrier 50 without causing an undesirable pressure drop.

While the interleaved barrier 50 of FIGS. 3-4 may offer significant noise reduction for blower units 12, the manufacturing of rows of structures 52 and 54 with such a complicated, overlapping geometry may prove difficult. Therefore, an alternative and easily manufactureable arrangement for the noise reduction barrier 50 may be possible. One such alternative barrier 50, with the rows of structures 52 and 54 made from parallel plates, is illustrated in FIG. 5. The structures of rows 52 and 54 include thick layers of reticulated foam 66 added to the left side of all the structures in order to absorb any noise 60 that approaches the structures. Air may pass through the barrier 50, as indicated by arrows 30, 32, and 34, but any noise 60 entering a space between the second row structures 54 may be absorbed by the foam 66 attached to the adjacent first row structure 52. As previously mentioned, the structures of the first row 52 align with spaces between the structures of the second row 54, and to ensure adequate absorption and redirection of the noise 60 by the rows 52 and 54, the structures of the rows overlap. That is, the height (H) 68 of each structure of the first row 52 is greater than the corresponding space (S) 70 between subsequent structures of the second row 54, and vice versa. This forms an overlap (O) 72 on either side of each structure, which may be defined by the following equation: O=(H-S)/2.

FIG. 3 and FIG. 5 illustrate two possible cross sectional shapes for the rows of structures 52 and 54 of a noise reduction barrier 50, and many other arrangements are possible, as will be apparent to those skilled in the art. For example, the structures may feature side surfaces that are positioned at an angle less than ninety degrees from the vertical plane. In addition, the cross sections of and spaces between different structures or rows may be nonequivalent, but the structures of the first row 52 may still be aligned with spaces between the structures of the second row 54. Although many different arrangements of the barrier 50 may be possible, not all arrangements may work equally well for reducing noise output from different blower units 12. Accordingly, the desired geometry of the rows 52 and 54, arrangement of reticulated foam 66, and ratios of structure thickness to foam thickness may be determined through acoustical calculations, numerical analysis, experimental testing, or a combination thereof.

A cross sectional side view of a second embodiment of noise reduction system for a modular AC unit 10 is shown in FIG. 6. A noise producing condenser fan 22, located in a condenser inlet 74, draws air from outside the AC unit 10, as indicated by arrows 76 and 78, and blows the air over condenser coils (not shown). Upon moving over the condenser coils, the air heats up and exits the condenser module 16 through louvers 26 in the top surface of the condenser module 16, as indicated by arrow 80. Due to the location of the condenser fan 22 in the inlet 74, a noise reduction barrier 50 as described in the previous embodiment would likely create a large and undesirable pressure drop across the inlet 74, caused by air being forced through the small spaces of the barrier 50. Instead of a barrier placed directly over the fan 22, the noise reduction system of FIG. 6 includes a noise redirecting structure 82 positioned a distance 84 away from the fan 22. This redirecting structure 82, shown as a wall in FIG. 6, is built to redirect the noise 60 coming from the condenser fan 22 toward one or more resonance chambers placed atop the condenser module 16. Although not illustrated, layers of reticulated foam 66 may be added to the surface of the redirecting structure 82 facing the AC unit 10 to reduce the amount of noise requiring attenuation by the resonance chambers.

Although the redirecting structure 82 is shown as a wall, the structure 82 may be any physical structure capable of changing the direction of sound pressure waves caused by the fan 22 toward the top of the AC unit 10. FIG. 7 illustrates certain features of the same noise reduction system, but with a scoop-shaped noise redirecting structure 82. The scoop shape may be more effective at redirecting the noise 60 coming from the fan 22 than a wall, and the structure 82 may coupled with the outer surface of the condenser module 16, maintaining the portability of the entire AC unit 10. Both illustrated embodiments of the structure 82 allow air to be drawn into the condenser module 16 from the space between the AC unit 10 and the structure 82. In this way, no severe pressure drop may occur across the fan 22. In addition to the noise redirecting structure 82, an additional wall (not shown) may be placed between the two condenser fans 22 and 24 to isolate the airflow toward each fan and the noise 60 coming from each fan. Such a wall may extend from the condenser inlet 74 to the noise redirecting structure 82, aligned perpendicular to the inlet 74, and the wall may be lined with reticulated foam 66 in order to absorb additional noise 60.

Resonance chambers 86, 88, and 90 are located above the condenser module 16, with openings facing the structure 82 in order to capture and attenuate the noise 60 exiting the condenser module 16. Waveforms of the noise 60 may enter the chambers 86, 88, and 90, reflect off the walls of the chambers, and combine with other incoming noise waveforms of the same frequency, canceling the noise 60. The first chamber 86 may be optimized to eliminate the noise 60 at the natural frequency of the fan 22, while the third chamber 90 may be optimized to eliminate the noise 60 at other harmonic frequencies of the fan 22. The second chamber 88 may be designed to attenuate the noise 60 at any other frequencies. The first chamber 86 and the second chamber 88 feature layers of reticulated foam 66 placed on certain chamber surfaces to absorb noise 60, and the first chamber 86 features a relatively small opening with a punched hole plate 92 covering the opening. FIG. 8 provides a front view of the punched hole plate 92, which may be metal or any other suitable material for allowing desired noise waveforms into the first chamber 86.

It should be noted that many other sizes, shapes, arrangements, and materials of the chambers 86, 88, and 90 may be possible and appropriate for attenuating noise 60 from condenser fans 22 and 24. For example, more chambers may be placed atop the condenser module 16 to attenuate more noise 60 from the condenser module 16. Alternatively, larger chambers may be used, the larger chambers affording a greater volume for the destruction of more noise 60. Furthermore, certain chambers may include foam placed on different surfaces and/or punched hole plates 92 placed in the chamber entrance. Several variations in chamber design are possible, and an appropriate chamber design for attenuating noise from any particular condenser module 16 may be optimized through calculations and testing to yield a desired level of noise reduction.

While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. 

1. An air conditioning noise reduction system, comprising: a base unit; an air inlet disposed on an outer surface of the base unit and configured to permit the passage of air therethrough; at least one fan disposed in the base unit and configured to draw air from outside the base unit through the inlet and to propel the air toward a downstream process; and a barrier disposed over the inlet and configured to permit passage of air from outside the base unit to the at least one fan but to prevent noise caused by the at least one fan from escaping the base unit, the barrier comprising two parallel rows of spaced structures wherein the structures of one row align with spaces between the structures of the other row.
 2. The noise reduction system of claim 1, wherein the barrier comprises a cover having two edges configured to couple with the base unit, the spaced structures being secured to the edges.
 3. The noise reduction system of claim 1, wherein the barrier comprises reticulated foam for absorbing the noise.
 4. The noise reduction system of claim 1, wherein the structures of one row overlap the structures of the other row.
 5. The noise reduction system of claim 1, wherein the structures of the two rows comprise side surfaces that interleave to form a channel-like structure between the two rows.
 6. The noise reduction system of claim 1, wherein the structures of both rows comprise parallel plates.
 7. The noise reduction system of claim 1, wherein the downstream process comprises an air conditioning, heating, ventilating, or refrigeration process.
 8. An air conditioning noise reduction system, comprising: a first row of spaced structures configured to redirect noise caused by a blower disposed in an air conditioning unit; a second row of spaced structures configured to redirect noise caused by the blower, the structures of the second row overlapping spaces between the structures of the first row; and one or more edges coupled to the structures of both the first row and the second row and configured to couple with a surface of the air conditioning unit such that air drawn by the blower is permitted to pass through spaces between the structures and to enter the air conditioning unit.
 9. The noise reduction system of claim 8, comprising reticulated foam disposed on surfaces of the first row and the second row of structures for absorbing noise from the blower.
 10. The noise reduction system of claim 8, wherein each row of structures comprises sheet metal.
 11. The noise reduction system of claim 8, wherein the structures of each row comprise equivalent shapes.
 12. The noise reduction system of claim 8, wherein the structures of both rows comprise parallel plates.
 13. The noise reduction system of claim 8, wherein the structures of the two rows comprise side surfaces that interleave to form a channel-like structure between the two rows.
 14. An air conditioning noise reduction system, comprising: a base unit; at least one fan disposed in the base unit and configured to draw air from outside the base unit and propel the air toward a downstream process; one or more resonance chambers disposed adjacent to an air inlet of the base unit and configured to attenuate noise caused by the at least one fan; and a structure disposed outside the base unit and configured to redirect noise toward the resonance chambers.
 15. The noise reduction system of claim 14, wherein the structure comprises a wall.
 16. The noise reduction system of claim 14, wherein the structure comprises a scoop.
 17. The noise reduction system of claim 14, comprising reticulated foam disposed over surfaces of the resonance chambers.
 18. The noise reduction system of claim 14, comprising one or more punched hole plates disposed over openings of the resonance chambers.
 19. The noise reduction system of claim 14, wherein the resonance chambers are configured to attenuate noise at a natural frequency of the at least one fan and/or harmonics of the fan noise.
 20. The noise reduction system of claim 14, wherein the downstream process comprises a condenser. 